Prior art bag emptying apparatuses of this type are disclosed in, for example, Ser. No. 421,063, Ser. No. 402,574, Ser. No. 404,170 and U.S. Pat. No. 4,181,461 and comprise, in principle, a receiving unit into which unopened bags are supplied manually or otherwise and in which a first cutting of the bags may occur, a cutting and feeding unit in the form of a horizontal screw conveyor having a casing and a cutting and feeding screw rotatably mounted therein for cutting the bags supplied into the receiving unit and for horizontally feeding the cut bags, and a separating unit connected to the discharge end of the screw and adapted to separate the contents from the bags cut by the screw.
In the prior art apparatuses according to the above-mentioned patent specifications, the bottom of the screw conveyor casing is provided with perforations or the like for removing from the casing any material which, during the cutting and transport by means of the screw, spills from the but bags onto the bottom of the casing while the bags are being conveyed toward the discharge end of the casing. However, although some material thus is separated within the cutting and feeding screw conveyor, the actual separation of the contents from the cut bags occurs according to prior art technique in the said separating unit which, in the above-mentioned patent specifications, is a relatively large cylindrical screening drum, the entrance end of which is connected to the discharge end of the screw conveyor for receiving the bags cut by the screw, and the opposite end of which is open for discharging emptied bags. To effect the separation within the screening drum, the drum is rotatably mounted about its geometrical axis and provided throughout its circumference with perforations or the like. To advance the cut bags through the screening drum during the separation therein, the axis of rotation of the drum may be slightly inclined toward the horizontal plane, or the screening drum may be provided on its inner circumference with blades or the like for advancing the bags as these are being tumbled about in the screening drum.
The contents separated from the bags are collected conventionally underneath the screening drum and/or the casing, and the emptied bags are discharged at the other end of the screening drum for collection, optionally for compaction in a separate collecting receptacle.
A bag emptying apparatus of the type described above has a number of disadvantages. Because complete separation requires both a screw conveyor and a separate screening drum having a relatively large diameter, the apparatus will be bulky and complicated. If, in addition, compaction of the emptied bags is desired, a separate compacting unit must be provided for this purpose at the discharge end of the screening drum, which further increases the size of the apparatus and makes its construction more complicated and costly. The considerable dimension and cost of a bag emptying apparatus of the type described implies that such an apparatus can be economically operated only by users who have frequent use for rapid emptying of many bags at a time. For users who have less frequent use for bag emptying and to whom the emptying time is not of decisive importance, these known apparatuses are not economic, for which reason the bags in this instance often are emptied manually. Furthermore, the use of a large screening drum frequently causes environmental pollution by the dust it raises.
When the material is discharged through the perforations in the screw conveyor casing and through the circumference of the screening drum, means are required for collecting the discharged material at one and the same location, which further contributes to increasing the cost and dimension of the apparatus.